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ESP32 GPIO Routing (Pin Mux)

Unlike classic microcontrollers (e.g., AVR, older STM32), the ESP32 chip has a fully configurable GPIO Matrix. This means most internal peripherals (UART, SPI, I2C, PWM, I2S) can be routed to any physical microcontroller pin!

Standard Pins (Input/Output)

GPIO: 0-19, 21-23, 25-27, 32-33

Can be used for anything (I2C, SPI, UART, PWM). They have internal Pull-Up / Pull-Down resistors.

⚠️ Input ONLY Pins

GPIO: 34, 35, 36 (VP), 39 (VN)

Cannot act as outputs! They do not have internal Pull-Up/Pull-Down resistors. Use only for ADC reading or as buttons (external pull-up resistor required).

⚠️ Pins Connected to Flash (Do not touch!)

GPIO: 6, 7, 8, 9, 10, 11

These pins physically connect the ESP32 chip to its SPI Flash memory chip. Connecting anything external to them will immediately crash the processor (Crash/Guru Meditation).

Strapping Pins (Boot Configuration)

GPIO: 0, 2, 5, 12, 15

During boot, the processor checks the state of these pins to determine the operating mode (e.g., entering UART flashing mode). Avoid connecting motors or pull-ups to them, as you will block code uploading.